System for hydroponically growing plants, apparatus and method therefor

ABSTRACT

The present invention provides a system for growing plants without soil, comprising a container ( 1 ) for containing a plant liquid nutrient reservoir; a support unit ( 2; 22 ) mounted in the container ( 1 ) above the floor thereof and extending substantially horizontally therein for supporting a plant to be grown; a lid for the container provided with a plant growth aperture ( 13 ) for the plant to grow up through; means ( 20; 34 ) for continuously circulating the plant liquid nutrient and for maintaining flow thereof in association with the support unit ( 2; 22 ); means for emptying and charging the plant liquid nutrient reservoir. The invention also includes a method of growing plants utilizing such a system.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application ofInternational Application PCT/GB01/00745, filed Feb. 21, 2001, whichinternational application was published on Aug. 30, 2001 asInternational Publication WO 01/62074. The International Applicationclaims the priority of British Patent Application 0004199.6, filed Feb.22, 2000.

FIELD OF THE INVENTION

The present invention relates to a system for hydroponically growingplants, and to an apparatus and method therefor. Hydroponic gardeningrelates to the growth of plants for aesthetic appeal and/or for foodproduction without the use of soil.

PRIOR ART (BACKGROUND)

Hydroponics has developed from the findings of experiments carried outto determine what substance makes plants grow and the composition ofplants. Such work on plant constituents dates back as early as the1600s. However, plants were being grown in a soil-less culture farearlier than this. Hydroponics is at least as ancient as the Egyptianpyramids. A primitive form has been carried on in Kashmir for centuries.The process of hydroponic growing in our oceans goes back to about thetime the earth was created. Hydroponic growing preceded soil growing.But, as a farming tool, many believe it started in the ancient city ofBabylon with its famous hanging gardens, which are listed as one of theSeven Wonders of the Ancient World, and was probably one of the firstsuccessful attempts to grow plants hydroponically.

Hydroponic gardening probably first became a modem reality around 1940when the U.S. Army used hydroponic gardening techniques to grow freshvegetables in the Pacific Islands. NASA was instrumental in advancingthe field of hydroponics. They were developing a way to cultivate foodin space in the absence of light. One of the major factors was the costof putting these materials into space. They developed hydroponicssystems as they are light, extremely efficient and have high yields.There are a number of fully-fledged hydroponics systems in a number ofAmerican nuclear submarines, Russian space stations and variousoff-shore drilling rigs.

The development of plastics materials freed growers from the costs ofconstructions associated with the concrete beds and tanks previouslyused. Beds are now scraped out of the underlying medium and simply linedwith a heavy vinyl (20 mm), then filled with growth medium to supportthe plants. With the development of suitable pumps, time clocks, plasticplumbing and other equipment, the entire hydroponic system can now beautomated, or even computerised, reducing both capital and operationalcosts.

Recently, interest in hydroponics gardening has substantially increased.The reasons for this probably include: firstly some of the majorcountries of the world continue to have problems producing food undertypical conditions—either because of poor weather or poor soil, or both.Secondly, in very populated areas, the availability of land for gardensfor the average homeowner is rapidly decreasing. Hydroponic gardeningtechniques offer the possibility of home-grown food products to thetownhouse apartment owner, or the owner of a small home with little landwho cannot otherwise have a garden.

There are two main types of hydroponic systems: an open system and aclosed system. In the open hydroponic systems, a nutrient solution isperiodically fed to the plants supported in an inorganic growth medium.The nutrient solution is drained through the growth medium to theenvironment. In the closed hydroponic system, the nutrient solution isperiodically fed to the plants supported in an inorganic growth mediumand then collected and recirculated for further use in later periodicfeeling cycles. Closed systems are preferred for being moreenvironmentally friendly, less wasteful of nutrient solution and hencemore economic. On the other hand, they suffer from the disadvantage thatthe recirculated solution deteriorates with each cycle, both in terms ofthe amount of nutrient available to the plant (which can be topped up)and in terms of the amount of waste products and contaminants that buildup, necessitating periodic flushing-out and cleaning of the closedsystem.

A typical example of a hydroponics system usable in either open orclosed forms comprises a plant supporting chamber having an inert growthmedium therein; a collection reservoir positioned below the plantsupporting chamber; a pump reservoir for containing a nutrient solution;and a valve/connection system delivering the nutrient solution to theplant supporting chamber and for operating the system in either open orclosed forms.

However, the presence of the inert, plant growth medium in suchhydroponics systems gives rise to problems that have an adverse effecton the system and, in particular, the plant and its growth. Suchproblems include build-up of inorganic salts or other plant waste,fluctuations in nutrient available, root rot and excessive root growth.Other problems include build-up of algae and widely fluctuating pH ofthe nutrient solution due to accumulation of waste in stagnant pocketsof nutrient solution. Therefore, there is a need for a simple systemthat avoids these problems, yet that provides an appropriate environmentfor growing plants without soil.

DISCLOSURE OF INVENTION

Accordingly, the present invention provides a system for growing plantswithout soil, which system comprises

-   -   (a) a container for containing a plant liquid nutrient        reservoir;    -   (b) a support unit mounted in the container above the floor        thereof and extending substantially horizontally therein for        supporting a plant to be grown;    -   (c) optionally, a lid for the container provided with a plant        growth aperture for the plant to grow up through;    -   (d) means for continuously circulating the plant liquid nutrient        and for maintaining flow thereof in association with the support        unit;    -   (e) means for emptying and charging the plant liquid nutrient        reservoir whereby a plant seed or bare-rooted plant seedling may        be supported in the support unit in the absence of growth medium        and may remain in contact with the flow of circulating plant        liquid nutrient, thereby growing hydroponically towards the        plant growth aperture and growing aeroponically in the        environment between the lid and the support unit.

Preferably, the system excludes the practical possibility of adding anyplant growth medium for supporting the plants.

Preferably, the circulating means comprising an electrical pump situatedon the floor of the container or in a separate housing connected to thecontainer. Suitably, the pump is one selected to operate in the range offrom about 60 litres/hour to about 180 litres/hour in the case of asingle container system. The pump may be selected so as to be able tocirculate air as well as water or other liquid nutrient. The systemaccording to this invention is suitable for both single and multipleuse, and for propagating and/or growing plants from seed or bare-rootedcutting.

For propagation purposes, the support unit is preferably trough-like,such as guttering or ducting or arcuate cross section over which thecirculating water flows. In this case, the single system preferably hasa plurality of plant growth apertures in the lid, whereby a plurality ofseeds may be propagated at once. However, for growth beyond thebare-rooted cutting stage, it is preferred that the support unitcomprises substantially a conduit, more preferably of square orrectangular cross-section, having therein one or more apertures in thetop (in use in the preferred embodiment, lid-facing surface thereof toallow overflow of the circulating water therefrom. Most preferably, theoverflow apertures are angular in plan view, and rounded or circularapertures should be avoided to prevent clogging by the plant roots.

The overflow aperture(s) preferably comprise(s) either a slot runninglaterally along a major part of the length of the support unit or aplurality of smaller slots or rectangular-, such as square-, shapedcut-outs therealong.

In the system for growing plants, rather than for propagating only, thesupport unit is preferably connected via a plant liquid nutrient conduitto the pump or other circulating means, whereby the plant liquidnutrient may be continuously circulated through the support unit and outvia the overflow aperture(s) into the container, from which it isre-circulated to the support unit.

The support system may itself comprise more than one support unit percontainer. Accordingly, the present invention further provides a systemcomprising a plurality of support units mounted in the container abovethe floor thereof and extending substantially horizontally therein forsupporting a plant to be grown. The support units may be arranged in astepped configuration.

Conveniently, there is provided, in association with the support unit,means for emptying it of liquid nutrient. Preferably, such meanscomprises a support conduit from the inside of the support unit, througha side face of the container, from which the system can be drained. Inthe case of a system comprising a plurality of containers, thecirculating means may be provided in a separate housing and may belinked to each other container via a plurality of plant liquid nutrientsconduits that, for example, connect to the support conduit which, inthis case, acts as a system fill, rather than a system drainage,conduit. In this case, drainage may be effected, for example, byprovision of an outlet towards the base of the container which mayitself be linked via one or more drainage conduit(s) to a centralreservoir tank, draining tank or (if an open system is desired) to theenvironment.

In the system according to a preferred embodiment of the presentinvention, the provision of a lid having minimal aperture dimensionswhen in use is an important feature, since this allows the plant(s) togrow aeroponically in the moist air that will accumulate, in use, in theenvironment between the support unit and the lid. If the lid aperturesare too large, then the moisture will escape and plant growth will notbe as effective. Accordingly, where necessary, plugs may be provided forthe lid apertures, particularly if the lid comprises a fill aperture forcharging the container with plant liquid nutrient. For similar reasons,the plant growth aperture may be provided with means for closing anygaps in the aperture between the plant and the surrounding lid.Preferably, the system is sealed when in use.

In use, the lid may be positioned substantially horizontally in the topof the container(s) or may be adapted to be placed angularly therein,particularly in the case where a stepped or shelving additional supportis associated with the support conduit. Accordingly, the faces of thecontainer(s) are appropriately sized, and the upper vertices thereof maybe angled to accommodate stepped or shelved additional support means.

Particularly in the case of an elongate container, there may be morethan one lid per container in the system.

As well as the lid, the support unit is another important feature of thesystem according to this invention. In prior art systems, the plants aresupported by a growth medium comprising rockwool or the like, whichgives rise to many of the problems mentioned hereinbefore. However, nosuch growth or support medium is required in the present system forsuccessful plant growth from seed through bare-rooted seedling toimmature plant (leaves, stem, roots) and finally fully-mature, such asflowering or fruiting, plant. It has been found surprisingly, that thesupport unit, with liquid nutrient flowing therethrough, providesexcellent physical support for the growing plant, whose root systemincreasingly adapts to wrapping around the unit, thereby anchoring theplant in the container. The weight of the growing plant is thereforeborne by the support unit. If desired, optionally, a water-permeable orpenetrable covering may be provided over the overflow aperture(s) on thesupport unit, such as a covering of synthetic, polymeric material, suchas a polyester/nylon woven sheet, such as is sold under the trade nameTERRAM, to aid anchorage.

Since no growth/support medium is required, the roots do not rot whenthe plant reaches the end of a growing cycle (eg finishes flowering),and removal of the plant does not cause damage to the root system, whichis particularly advantageous in the case of edible roots or roots thatmay otherwise be commercially important. In the case of edible roots,such as tubers or the like, an additional root support may be providedbelow the support unit in order to take the weight of such rootvegetables as potatoes, swedes and the like. This additional rootsupport may comprise a hammock of a water-permeable or penetrablecovering of the same or a similar material as that described above forthe optional support unit covering, slung underneath the support unitand suspended from each end thereof. Alternatively or as well, thesupport unit may further comprise additional support means in the formof stepped or shelving elements, extending downwardly from the base ofthe support unit. Such stepped or shelved support means may comprisesubstantially horizontal and flat shelves or platforms, or may comprisegutter-like support means for the foot system.

The support unit(s) for use in the container(s) comprising the systemaccording to this invention therefore preferably comprise at least oneconduit for the flow-through of the plant liquid nutrient havingaperture(s) in an upwardly- or lid-facing (in use) surface thereof, andoptionally other plant-supporting surfaces in association with saidconduit.

The plant liquid nutrient for use in the system of this invention maycomprise water only, or a mixture of water and a conventional or knownplant liquid feed or liquid fertiliser. For propagation and the earlystages of plant growth from seed or bare-rooted cutting, water alone maysuffice. Whereas in prior art systems, emptying of the system andrecharging with nutrient is required and cumbersome, in the presentsystem, the liquid feed can simply be administered alone or in aqueoussolution to the container or tank reservoir without the need fordrainage. Repeated emptying and recharging of this system is notnecessary, as it is clean, simple to use, and adaptable to each stage ofthe plant's life cycle.

It has also been found, surprisingly, that, in addition to ease ofhandling, growth of plants in the system according to the invention isaccelerated compared to that using conventional soil methods. Forexample, sweetcorn (maize) planted about 5 cm below ground will normallytake about a week to appear above the surface, whereas the same stage isreached in about 48 hours using the system according to the invention,and in about 5 days the sweetcorn has grown equivalent to about 3 weeksin the soil. Other advantages include the quality of the plants producedby the system according to the invention being superior to those grownby other methods. In particular, we have observed that the leaves ofstrawberry plants grown in our system are consistently fatter and juicerthan seedlings seen in garden centers.

The present invention therefore further provides a method for growingplants without soil, which method comprises

-   -   (a) placing a plant, such as a seed or seedling, in the absence        of plant growth medium on a plant support unit of a system        according to this invention;    -   (b) charging the container with sufficient plant liquid nutrient        to enable circulation thereof and to maintain flow therefor in        association with the support unit;    -   (c) preferably, fitting the lid to the container; and    -   (d) activating the circulating means.

Optionally, the method may further comprise

-   -   (e) topping-up the container with further plant liquid nutrient        and/or a different liquid nutrient.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example only, withreference to the accompanying drawings in which

FIG. 1 is a perspective view of a single container of a multiplecontainer system according to a first preferred embodiment of theinvention wherein FIG. 1A is a partly-exploded view through thecontainer with lid raised, and FIG. 1B is a perspective view of thesystem in use;

FIG. 2 is a vertical cross-section through the system of FIG. 1, whereinFIG. 2A is a section depicting a sectional side view of the supportunit, and FIG. 2B is a section depicting a sectional end view of thesupport unit.

FIG. 3 is a plan view of the system of FIG. 1, wherein FIG. 3A shows thelid open/absent; and FIG. 3B shows the lid in place.

FIG. 4 is a side elevation of the lid of the system of FIGS. 1 to 3; and

FIG. 5 is a partially-exploded perspective view of a multiple plant,single container system according to a second preferred embodiment ofthe invention, with the lid raised; and

FIG. 6 is a section corresponding to FIG. 2B showing the support unitsarranged in stepped configuration.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 to 4: one embodiment of the invention is for use ingrowing a single plant comprising a container (1) of heavy dutyplastics, which has been blow-molded using conventional technology.Alternatively, the container may be of any material suitable for thepurpose, such as terracotta, pottery, concrete, brick or the like.Within the container (1), leaving a margin between it and the lid (3)when in use, a support unit (2) is mounted on solid supports (6, 7) onopposing walls of the container (1). The support unit (2) is made e.g.from ABS plastic and spans the width of the container (1) betweenopposing walls thereof; forming a square-section, hollow bar. One end ofthe support unit (2) is connected to a support pipe (5) to which may beconnected (not shown) either a tap or other drainage system for emptyingthe system when the container is to be used as a stand-alone, singleplant system or a fill connector or other supply system leading to theliquid nutrient reservoir/pumping station when the container is to beused as part of a multiple-container system. At the opposite end, in aside-wall of the support unit (2), is a nozzle (8), which may be eitherplugged or blank, or to which a feed pipe (not shown) may be connectedin the case of a stand-alone, single plant system. Just above the floorof the container (1), in a side-wall thereof, is a further nozzle (9)for connecting the container via a connector system (not shown) fordrainage to other container(s) when used as part of a multi-containersystem or may be plugged in the case of a stand-alone single containersystem.

Also provided is a shelf (10), shown only in FIG. 2, for supporting e.g.tubers and the like underneath the support unit (2). In the top of thesupport unit (2) is a slot (11) extending about two-thirds of the wayalong its length across the container (1) whereby, in use, the water orother liquid feed (12) provided in the container 91) may flow throughthe support unit (2) either via connector (8) or via support pipe (5)and overflow from the slot (11). In the case of the stand-alone, singlecontainer system, the connector (8) connects via a conduit/piping to anelectrical pump (20) (shown schematically only) positioned on the floorof the container. The lid (3) is sized to fit snugly and water-tightlyinto the top of the container (1) and has an aperture (13) therein forthe plant to grow up through, as illustrated in FIG. 1B. The aperture(13) occupies a central position in the lid (3) of a single plantcontainer, above the support unit (2) and the slot (11) therein.

Referring now to FIG. 5, illustrating a multi-plant, elongate container(21), the support unit (22) requires additional transverse mounts (26)that extend within the container (21) at regular intervals. In thisembodiment, the overflow is provided by multiple slots (31), also atregularly-spaced intervals along the length of the container (21). Apump (34) is placed on the floor at one end of the container (21) and isconnected via flexible piping (35) to the support unit (22). An elongatelid (23) is provided with an elongate slot (33) along substantially allof its length for the plants to grow up through (not shown). Thecontainer may be filled through the lid aperture (33). This container(21) may also be adapted, as described for the embodiment of FIGS. 1 to4, for multiple container use.

FIG. 6 shows the previously described embodiment of the inventionwherein a plurality of support units (222) each extend horizontallyacross the container (1) in a manner similar to the support unit (2) ofthe embodiments depicted in FIGS. 1-4. In FIG. 6, the support units(222) are arranged in a stepped configuration at different levels abovethe base of the container (1) as shown.

1. A system for growing plants without soil, the system comprising: (a)a main container, said main container having an open top and a baseproviding a plant liquid nutrient reservoir; (b) an elongate supportunit mounted in said main container for physically supporting a plant orplant seed to be grown, said elongate support unit comprising a conduitmounted below said top and above said base to extend substantiallyhorizontally across said main container, said elongate support unithaving a top surface providing a support surface for the plant or plantseed, said elongate support unit defining an outer surface spaced inwardfrom said main container to allow the growing plants to wrap around theelongate support unit; (c) means for continuously circulating a flow ofliquid nutrient to said support unit for supplying liquid nutrient to aplant or seed supported by said support unit, said circulating meansbeing arranged to flow the liquid nutrient across said support surfacefor supplying the plant or seed with nutrient; (d) means for chargingsaid liquid nutrient reservoir; and (e) a close fitting lid for closingsaid main container to provide an enclosed space within said maincontainer where a moist atmosphere can accumulate and where a plant orseed can grow, said lid being formed with a plant growth aperture forthe plant to grow up through; (f) whereby in use a plant seed orbare-rooted plant seedling may be supported on said support unit in theabsence of growth medium and may remain in contact with the flow ofcirculating liquid nutrient, so that the roots of the plant seed orseedling wrap increasingly around said support unit to anchor the plantin the container, and the plant seed or seedling grows bothaeroponically in the environment between said lid and said support unitand hydroponically towards said plant growth aperture; (g) wherein saidtop surface of said elongate support unit has at least one aperturetherein to allow overflow of the plant liquid nutrient therefrom.
 2. Asystem according to claim 1 in which said conduit is of substantiallysquare or rectangular cross section.
 3. A system according to claim 2 inwhich said at least one overflow aperture comprises a slot extendinglongitudinally of said conduit.
 4. A system according to claim 2 inwhich said at least one overflow aperture comprises one of an elongateslot extending along a major part of the length of said conduit and aplurality of short slots or cut-outs running along a longitudinal axisof said conduit.
 5. A system according to claim 1, further comprising awater-permeable covering over at least a portion of said support unit.6. A system according to claim 1, in which said plant growth aperture insaid lid is of minimal dimensions for retaining moisture in said maincontainer.
 7. A system according to claim 1, in which said maincontainer is trough-like, and said lid and said plant growth apertureare elongate.
 8. A system according to claim 1, having a plurality ofsaid support units mounted within said main container above said base,each said support unit extending substantially horizontally across saidmain container for supporting plants to be grown.
 9. A system accordingto claim 8, in which said support units are arranged in a steppedconfiguration.
 10. A system according to claim 1, further comprising asupport conduit connected to the inside of said support unit andarranged to support said support unit within said main container.